Reversible piston hammer for percussion tool

ABSTRACT

A pneumatic percussion tool having a reciprocable piston hammer with similar reduced diameter portions extending from opposite sides of an enlarged piston portion. Each reduced diameter portion includes an annular groove cooperable with associated inlet porting for admitting pressure air to act on the piston to deliver a percussion blow. The respective grooves are located at different positions with respect to the opposite impact end faces of the piston hammer and the hammer can be reversibly disposed in the tool cylinder to provide variable impact blow, blow frequency, and air consumption.

United States Patent Palauro [451 Sept. 25, 1973 REVERSIBLE PISTON HAMMER FOR PERCUSSION TOOL Dieter K. Palauro, Denver, Colo.

Gardner-Denver Company, Quincy, 111.

Filed: Aug. 18, 1972 Appl. No.: 281,725

Inventor:

Assignee:

US. Cl 173/134, 91/54, 92/59, 173/29 Int. Cl. F01b 29/04 Field of Search 173/105, 115, 134, 173/29; 92/1341, 59; 91/277, 54

References Cited UNITED STATES PATENTS 9/1920 Smith 173/134X 11/1914 Wafker 173/29 1,848,340 3/1932 Gilman 173/105 X Primary ExaminerMarvin A. Champion Assistant Examiner-Wil1iam F. Pate, Ill Att0rneyM. E. Martin 57 ABSTRACT A pneumatic percussion tool having a reciprocable piston hammer with similar reduced diameter portions extending from opposite sides of an enlarged piston portion. Each reduced diameter portion includes an annular groove cooperable with associated inlet porting for admitting pressure air to act on the piston to deliver a percussion blow. The respective grooves are located at different positions with respect to the opposite impact end faces of the piston hammer and the hammer can be reversibly disposed in the tool cylinder to provide variable impact blow, blow frequency, and air consumption.

5 Claims, 2 Drawing Figures BACKGROUND OF THE INVENTION Fluid operated percussion tools such as rock drills and the like of the type wherein the reciprocating piston hammer includes passage means for valving fluid to actuate itself are generally well known. An example of such a percussion rock drill is disclosed in US. Pat. No. 3,666,024 to R.W. Beaumont. Such types of fluid operated tools are also sometimes characterized by a piston hammer which includes reduced diameter portions having impact striking faces extending axially on opposite sides of an enlarged piston portion. Such piston hammers may be reversibly'disposed in the drill cylinder bore in the event that damage to one of the striking faces should be incurred as suggested in US. Pat. No. 1,293,225 to W.A. Smith. Heretofore, the abovementioned general type of percussion rock drill has not been capable of convenient adaptation to operate at various blow frequencies or to efficiently utilize the available pressure fluid supply without interchanging internal drill parts. This is not only inconvenient but is costly in terms of requiring extra parts to be kept available when it is desired to change the impact blow, blow frequency, or to more efficiently utilize the available pressure fluid quantity.

SUMMARY OF THE INVENTION The present invention provides for a pressure fluid operated percussion rock drill characterized by a reversible piston hammer of the type which includes passages for valving pressure fluid to the drill cylinder and which may be reversibly disposed in the drill cylinder to change the percussion blow frequency.

With the fluid operated percussion rock drill of the present invention, variable impact blow, blow frequency, and pressure fluid utilization may be easily attained by reversing the arrangement of the piston hammer in the drill cylinder.

Moreover, with the present invention pneumatic rock drills of the general type disclosed may be easily adapted to operate more efficiently at various altitudes or may be adapted to more efficiently utilize the available supply of pressure air for work purposes.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal section view of a fluid operated percussion rock drill in accordance with the pres- 'ent invention.

FIG. 2 is a longitudinal view of the piston hammer of the drill illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2 of the drawing the present invention is embodied in a fluid operated percussion tool generally designated by the numeral 10. The tool is commonly known as an independent rotation pneumatic percussion rock drill and includes a cylinder housing 12 having a bore 14. The cylinder 12 is disposed between a backhead housing portion 16 and a housing portion 18 suitably secured together by elongated side rods 20 and 22. The side rods 20 and 22 extend forwardly to secure a cover member 24 and a cap 26 in assembly with the previous mentioned drill housing portions. The housing portion 18 includes a chuck member 28 rotatably disposed in suitable bearings 30 and including means for supporting and rotatably driving an impact blow-receiving member 32 commonly known as a shank. The chuck member 28 is rotatably driven by a suitable fluid operated motor 34 which is drivably engaged to the chuck member by gearing 36..

- low interior 40 in which is secured a sleeve member 42.

The interior 40 is suitably adapted to be in communication with a source of pressure fluid such as compressed air. The sleeve 42 includes a reduced diameter bore 44 opening into the bore 14 and spaced annular passages 46 and 48 opening to the bore 44. Longitudinal passages 50 communicate the annular passage 48 with the interior 40. The annular passage 46 is in communication with radially extending passages 52 which in turn are in communication with an annular passage 54 in the backhead portion 16. The annular passage 54 in turn is in communication with a passage 56 leading to an annular passage 58 in the cylinder 12. The cylinder 12 also includes an annular passage 60 forming an exhaust port.

The percussion tool 10 further includes a reciprocable piston hammer generally designated by numeral 62 and characterized by an enlarged piston portion 64 having transverse faces 61 and 63 and closely fltted in the bore 14. The piston hammer 62 is also characterized by integral cylindrical stern portions 66 and 68 extending axially on opposite sides of the piston portion 64. The stem portions-66 and 68 are of equal diameter and substantially equal length and are respectively delimited by transverse end faces 70 and 72. In the arrangement shown in FIG. 1 the stem portion 66 is slidably supported by the sleeve 42 and the stern portion 68 is supported in bearing means formed by a sleeve 74 disposed in the housing portion 18. The stem portions 66 and 68 include first and second fluid conducting passage means disposed on the periphery thereof and comprising the respective annular grooves 76 and 78.

As shown by the position of the piston hammer 62 in FIG. 1 the groove 76 cooperates with the passage 48 in the sleeve member 42 to valve pressure fluid to the bore 14 to act on the piston face 61 to drive the piston hammer forwardly on a blow-delivering stroke. Pressure fluid supplied to the interior 40 acts on the end face 70 also. As the piston hammer 62 moves forwardly the end face 70 passes the edge of the annular passage 46 after the groove 76 has moved out of communication with passage 48 and provides for flow of fluid through passages 54 and 56 to act on the piston face 63 to reverse the direction of movement of the piston hammer at the completion of a blow-delivering stroke.

As the faces 61 and 63 pass the exhaust port 60 pressure fluid acting thereupon is exhausted from the bore 14. The aforedescribed operation of the percussion tool 10 is basically well known.

By removing the backhead member 16 from the cylinder 12 the piston hammer 62 may be removed and reversibly disposed in the bore 14 so that the groove 78 cooperates with passage 48 to valve pressure fluid into the bore to act on the face 63. The face 70 now becomes the striking surface for impacting the member 32. This provides for a versatile arrangement in the event that one of the striking faces becomes damaged.

Moreover, the axially projecting stern portions 66 and 68 support the piston hammer 62 in the drill and no sliding engagement of the piston portion 64 with the bore 14 is required and accordingly seizing or scoring of the cylinder and piston is substantially eliminated.

The grooves 76 and 78 are proportioned in such a way that the groove 76 is in communication with the passage 48 for a shorter distance of movement of the piston hammer 62 on its forward or blow-delivering stroke and accordingly, at a given pressure, less pressure fluid, such as compressed air, is valved into the cylinder bore 14 than when the piston hammer is disposed for the groove 78 to be cooperable with the passage 48. The grooves 76 and 78 are so proportioned that the edge of the groove 78 toward the face 72 is an axial distance x from the face 70 and the corresponding edge of the groove 76 is an axial distance y from the face 72, as shown in FIG. 2. The distance x is greater than the distance y.

The above described arrangement in a percussion tool may be advantageously used to satisfy various operating requirements of percussion rock drillsv In a percussion rock drill the elongated drill stem components and the bit portion may limit the work rate or power that may be produced by the drill to penetrate a rock formation or the like. Accordingly, if an adequate air supply is available to operate the drill at a given pressure with the groove 78 cooperable with the passage 48 and it is desired to use smaller diameter drill rods and bits the piston hammer 62 may be reversed to make the groove 76 cooperable with passage 48 whereby a lower blow frequency and work rate input to the drill rods may be obtained to avoid overheating and damage thereto. Moreover, ifa maximum available quantity rate of pressure air supplied to the drill at a desired pressure is less than the amount that is consumed with the piston hammer arranged for the groove 78 to be operable, the piston hammer can be reversely arranged in the cylinder so that the groove 76 is cooperable with passage 48 and the drill will consume the lower available air quantity while maintaining the desired operating pressure and concomitant impact blow energy. In this way with a supply of compressed air being derived from a compressor using ambient inlet air the piston hammer may be arranged to use the groove 76 when operating at higher altitudes without a reduction in impact blow energy.

Another advantage of the present invention which may be enjoyed in percussion rock drills is that when the supply rate of pressure air at a predetermined pressure is not sufiicient to maintain that pressure regardless of the arrangement of the piston hammer in the cylinder the piston hammer may be arranged to deliver lower impact blow energy and higher blow frequency with the groove 78 operable and a comparatively higher impact blow energy and lower blow frequency with the groove 76 cooperable with passage 48. In this way the drill 10 may be operated for more efficient rock penetration in accordance with the known condition that hard rock formations are more easily penetrated by comparatively higher impact blow and lower blow frequency.

What is claimed is:

1. In a fluid operated percussion tool:

a housing including a cylinder bore;

a blow-receiving member disposed in said tool;

a piston hammer adapted to be reversibly disposed in said cylinder bore for reciprocation therein to deliver repeated impact blows to said member;

passage means in said tool adapted to be in communication with a fluid pressure source;

said piston hammer including first passage means c0 operable with said passage means for valving pressure fluid to said cylinder bore to drive said piston hammer to impact said member, and second passage means cooperable with said passage means upon reversing said piston hammer in said cylinder bore for valving pressure fluid to said cylinder bore to drive said piston hammer to impact said member with greater frequency than when said first passage means and said passage means are cooperable.

2. The invention set forth in claim 1 wherein:

said piston hammer includes a piston portion and reduced diameter stem portions extending axially on opposite sides of said piston portion and including respective transverse end faces delimiting the axial length of said stem portions, said first passage means is disposed on one of said stem portions and said second passage means is disposed on the other of said stem portions.

3. The invention set forth in claim 2 wherein:

said tool includes a reduced diameter bore in said housing, said passage means opening into said reduced diameter bore and one or the other of said stem portions may be reciprocably disposed in said reduced diameter bore for cooperation of said respective first passage means or said second passage means with said passage means.

4. The invention set forth in claim 3 wherein:

said first passage means is disposed at an axial distance from the transverse end face delimiting said other stem portion which is less than the axial distance of said second passage means from said transverse end face delimiting said one stem portion.

5. The invention set forth in claim 4 wherein:

said first and second passage means comprise grooves disposed on the periphery of said stern portions. 

1. In a fluid operated percussion tool: a housing including a cylinder bore; a blow-receiving member disposed in said tool; a piston hammer adapted to be reversibly disposed in said cylinder bore for reciprocation therein to deliver repeated impact blows to said member; passage means in said tool adapted to be in communication with a fluid pressure source; said piston hammer including first passage means cooperable with said passage means for valving pressure fluid to said cylinder bore to drive said piston hammer to impact said member, and second passage means cooperable with said passage means upon reversing said piston hammer in said cylinder bore for valving pressure fluid to said cylinder bore to drive said piston hammer to impact said member with greater frequency than when said first passage means and said passage means are cooperable.
 2. The invention set forth in claim 1 wherein: said piston hammer includes a piston portion and reduced diameter stem portions extending axially on opposite sides of said piston portion and including respective transverse end faces delimiting the axial length of said stem portions, said first passage means is disposed on one of said stem portions and said second passage means is disposed on the other of said stem portions.
 3. The invention set forth in claim 2 wherein: said tool includes a reduced diameter bore in said housing, said passage means opening into said reduced diameter bore and one or the other of said stem portions may be reciprocably disposed in said reduced diameter bore for cooperation of said respective first passage means or said second passage means with said passage means.
 4. The invention set forth in claim 3 wherein: said first passage means is disposed at an axial distance from the transverse end face delimiting said other stem portion which is less than the axial distance of said second passage means from said transverse end face delimiting said one stem portion.
 5. The invention set forth in claim 4 wherein: said first and second passage means comprise grooves disposed on the periphery of said stem portions. 